In and around the mid north coast town of Taree, police helicopters winched residents from rooftops while boats were used to reach others trapped by rising waters.
More than 150 operations have been carried out so far.
Authorities say the rainfall over the Hunter and Mid North Coast has been relentless, with saturated ground and swollen rivers worsening the impact.
The Manning River in Taree surged past its 1929 record, peaking at 6.4 metres.
Thousands of residents have been cut off by floodwaters, others have lost power, and businesses have been inundated.
